1. Field of the Invention
The present invention relates to an illumination sensing device, and more particularly to an illumination sensing device that senses external light in a portable terminal.
2. Discussion of the Background
Generally, a portable terminal refers to a device utilized for wireless communication. Portable terminals may be used to provide various contents, such as television programs, on-line games, on-demand videos, etc. as well as voice communication service and short message service (i.e. text messages).
A portable terminal may be a bar-type terminal, flip-type terminal, or folder-type terminal according to its external structure. The bar-type terminal has a single housing with a communication circuit, a transmitter unit, a receiver unit, input/output units, etc. The flip-type terminal includes a flip cover in addition to the structure of the bar-type terminal. The folder-type terminal includes a pair of housings, and various elements including input/output units are included in the housings. A sliding-type portable terminal has recently emerged, so as to enhance, together with the folder-type terminal, the portability and convenience of the terminal and to satisfy various user requirements.
Portable terminals usually utilize a liquid crystal display (LCD) for their display unit. A user may easily recognize information displayed on the LCD when the LCD is in a bright environment. However, it may be difficult for a user to recognize information displayed on the LCD when the LCD is in a dark environment. Therefore, a light emitting diode (LED) may be used to provide additional illumination for the LCD. Such an LED is called a backlight unit, which usually provides illumination during a predetermined time interval when one surface of the terminal's housing is open to expose a keypad or one of the keys of the keypad is pressed.
However, the conventional backlight unit may provide illumination regardless of the environment in which the portable terminal is used. Therefore, the conventional backlight unit may consume a large amount of battery power, thereby reducing the terminal's stand-by and operating time.
In order to overcome such a problem, a portable terminal may be equipped with an illumination sensor that is mounted in the terminal's housing to receive and sense external light. Using the illumination sensor, it may be possible to achieve automatic backlighting control that is appropriate to the environment in which the portable terminal is used.
However, because the illumination sensor is mounted in the terminal's housing, the quantity of received light may change due to the distance between the housing and the illumination sensor's light-sensing surface, thereby disturbing exact operation of the illumination sensor.